OG SC 第四题请教

A  survey by the NCC showed that in 1986 there were 20.736 female ministers, almost 9 percent of the nation' clergy, twice as much as 1977

(A) ,,,

(B) ,,,

(C) double what it was in 1977

(D) double the figure for 1977

为什么不选C呢？figure for这种搭配对吗？XDF说double可以和what it was连用，但是OG里面说这个很wordy，我觉得这个和D不是差不多的吗？还是说这个可以选，只是D更好一些？